Degreasing of strip material by solvent vapour



K. A. HOLM 3,35 DEGREASING 0F STRIP MATERIAL BY SOLVENT VAPOUR Nov. 7, 1967 Filed March 5, 1965 I HI QI I IGINU H l l l l l h l i pwl w l l m l l lm l l h l l l wl l m United States Patent 3,350,734 DEGREASlNG 0F STRIP MATERIAL BY SOLVENT VAPOUR Kurt Anders Holm, Skoghall, Sweden, assignor to Uddeholms Aktiebolag, Uddeholm, Sweden, a company of Sweden Filed Mar. 3, 1965, Ser. No. 436,806 Claims priority, application Sweden, Mar. 6, 1964, 2,878/ 64 2 Claims. (Cl. 15-402) ABSTRACT OF THE DISCLOSURE The invention is concerned with an apparatus for degreasing strip material by means of vapour of a boiling solvent. The novelty of the invention resides in providing means for spraying liquid solvent onto the strip and wipers for rubbing off any excess of liquid solvent from the strip.

The invention relates to an apparatus for degreasing strip material by means of the vapour of a boiling solvent having a vapour which is heavier than air, for instance trichloroethylene and tetrachlorethylene. The apparatus is of the type comprising a container for the solvent, including a lower liquid zone having heating means for the boiling of the solvent and an upper vapour zone for the vapour of the solvent, cooling means in the upper portion of the vapour zone to define a substantially con stant boundary layer between air and vapour, and means for conveying the strip material into and out of the vapour zone.

In an apparatus as defined above the vapour of the solvent condenses on the strip material, which is introduced in a comparatively cold condition. The condensate dissolves grease on the strip and flows off the strip. It has been found, however, that the condensate does not have sufficient time for flowing off the strip completely, not even when the strip has a comparatively low velocity. This results in that the solvent accompanies the strip out of the vapour zone and, if conditions are disadvantageous, out of the degreasing apparatus. This involves a loss of solvent and also, in the latter case, health problems.

It has been found possible, according to the invention, to eliminate the risk that the strip shall leave the degreasing apparatus in a wet condition by providing wipers acting on both sides of the strip, said wipers being situated where the strip leaves the vapour zone, that is in the boundary layer between air and vapour. The position of the wipers is critical. If they are placed in the vapour zone additional vapour may condense on the strip after it has passed the wipers, resulting in solvent being carried up into the air and, perhaps, out of the apparatus. If the Wipers are placed in the air above the vapour zone stdvent will be carried up into the air, which is not desired. It has been found that the wipers shall preferably be positioned less than 50 millimeters from the boundary layer between air and vapour.

The upper surface of the vapour zone shall preferably be defined by an overflow for keeping the height of the boundary layer between air and vapour as constant as possible. Further, the heating means of the degreasing apparatus shall be dimensioned to keep the upper surface of the vapour zone at the height defined by the overflow during operation, that is, the heat supplied shall be greater than that required for heating the strip. The heavy solvent vapour will flow over said overflow and will then meet and condense upon cooling means, the condensate being returned to the container for the liquid solvent. The solvent shall preferably be returned by means of a pump "ice that sprays the solvent onto the strip in the vapour zone. This produces an improved cleaning action, in that solid particles which adhere loosely to the strip will be sprayed away from the strip.

The invention will be more closely described with reference to the accompanying drawing, which illustrates an embodiment of the invention.

A container 1 has in its bottom a zone 2 for liquid solvent. Said zone contains heating elements 4 for boiling the solvent. The vapour rises to a vapour zone 3, having its highest level defined by a wall 10. The upper edge of said wall 10 forms an overflow. The heavy solvent vapour flowing over said overflow meets cooling tubes 11 upon which the vapour condenses. The condensate flows to a tank 13 via a tube 12.

The strip 5 to be degreased is conveyed into the container 1 on rollers 7, is bent around a roller 6 in the vapour zone, and is conveyed out of the container on rollers 8. Suction boxes 9 are provided at the places where the strip enters and leaves the apparatus, to prevent solvent vapour from leaking out.

Wipers 14 are provided at the place where the strip 5 leaves the vapour zone 3. The wipers act upon the upper and lower sides of the strip, over its entire width. The wipers may consist of bristle, for instance from horsehair or nylon, or of a resilient lip, for instance from leather or plastics. The Wipers are positioned to touch the strip 5 in the level defined by the upper edge of the wall 10.

Two tubes 15 are provided in the vapour zone 3, between the roller 6 and the wipers 14. They extend horizontally along the entire width of the strip, on its upper and lower side. The tubes 15 are provided with perfora' tions or spray nozzles on the side facing the strip. The tubes 15 are connected, through a conduit 16, to a pump 17 which is fed with condensate from the tank 13. The conduit 16 is connected to the tank 13 via a valve 19, which is regulated by a float 20 in the tank 13. The valve 19 is opened when the surface of the solvent in the tank 13 is low, and is closed when the surface is high.

The apparatus described operates like this. The strip 5 is fed through the degreasing apparatus in the direction of the arrow. The solvent vapour begins to condense on the comparatively cold strip moving down into the vapour zone 3. The condensate dissolves grease on the strip and flows back to the liquid zone 2. The cleaning elfect is further improved by the condensate that is sprayed onto the strip through the tubes 15. If solvent remains on the strip leaving the vapour zone, said solvent is removed by the wiper 14. In this way the inter-mixing of air and vapour can be kept low, and so can the quantity of vapour that is lost through the suction boxes 9. On degreasing a thick strip a large quantity of solvent will condense on the strip. Consequently, the quantity of solvent condensing on the cooling tubes 11 and flowing to the tank 13 will be comparatively small, resulting in a lower liquid surface in the tank 13. The float 20 opens the valve '19, and part of, or the entire quantity of, the solvent from the pump 17 will be pumped into the tank 13through the tube 18. This provides a guarantee that the pump 17 will always be fed with solvent.

What is claimed is:

1. An apparatus for degreasing strip material, comprising a container, a first, lower zone in said container for a liquid solvent, heating means in said first: zone for boiling the solvent, a second, middle zone in said container for the vapour of said boiling solvent, cooling means in said second zone for defining a highest level of the vapour, a tank for receiving the solvent condensed on said cooling means a third, higher zone in said container, an inlet opening and an outlet opening for the strip in said third zone, means for conveying the strip from said inlet opening down into said second zone and up into said third zone and out through said outlet opening, wipers adjacent both sides of the path of said strip and adjacent the boundary between said third and second zones to rub off any remaining solvent from the strip passing from the second to the third zone, spraying means adjacent both sides of the path of the strip between said first zone and said Wipers and means for pumping solvent from said tank to said spraying means.

2. An apparatus as claimed in claim 1, in which said means for pumping solvent comprises a pump, a pipe connecting the inlet of said pump to said tank, a second pipe leading from the outlet of said pump to said spraying means, a conduit connecting said second pipe with said 4 which is connected to said valve for regulating it to keep a substantially constant level of liquid solvent in said tank.

References Cited UNITED STATES PATENTS CHARLES A. W'ILLMUTH, Primary Examiner.

tank, a valve in said conduit, and a float in said tank 15 L. G. MACHLIN, Assistant Examiner. 

1. AN APPARATUS FOR DEGREASING STRIP MATERIAL, COMPRISING A CONTAINER, A FIRST, LOWR ZONE IN SAID CONTAINER FOR A LIQUID SOLVENT, HEATING MEANS IN SAID FIRST ZONE FOR BOILING THE SOLVENT, A SECOND, MIDDLE ZONE IN SAID CONTAINER FOR THE VAPOUR OF SAID BOILING SOLVENT, COOLING MEANS IN SAID SECOND ZONE FOR DEFINING AHIGHES LEVEL OF THE VAPOUR, A TANK FOR RECEIVING THE SOLVENT CONDENSED ON SAID COOLING MEANS A THIRD, HIGHER ZONE IN SAID CONTAINER, AN INLET OPENING AND AN OUTLET OPENING FOR THE STRIP IN SAID THIRD ZONE, MEANS FOR CONVEYING THE STRIP FROM SAID INLET OPENING DOWN INTO SAID SECOND ZONE AND UP INTO SAID THIRD ZONE AND OUT THROUGH SAID OUTLET OPENING, WIPERS ADJACENT BOTH SIDES OF THE PATH OF SAID STRIP AND ADJACENT THE BOUNDARY BETWEEN SAID THIRD AND SEOCND ZONES TO RUB OFF ANY REMAINING SOLVENT FROM THE STRIP PASSING FROM THE SECOND TO THE THIRD ZONE, SPRAYING MEANS ADJACENT BOTH SIDES OF THE PATH OF THE STRIP BETWEEN SAID FIRST ZONE AND SAID WIPERS AND MEANS FOR PUMPING SOLVENT FROM SAID TANK TO SAID SPRAYING MEANS. 